CN114230363A - Preparation method of electromagnetic parameter adjustable porous carbon particle microwave absorbent - Google Patents
Preparation method of electromagnetic parameter adjustable porous carbon particle microwave absorbent Download PDFInfo
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- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 63
- 239000002245 particle Substances 0.000 title claims abstract description 58
- 239000002250 absorbent Substances 0.000 title claims abstract description 49
- 230000002745 absorbent Effects 0.000 title claims abstract description 49
- 238000002360 preparation method Methods 0.000 title claims abstract description 31
- 239000004917 carbon fiber Substances 0.000 claims abstract description 54
- 229920000049 Carbon (fiber) Polymers 0.000 claims abstract description 48
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 34
- 239000011148 porous material Substances 0.000 claims abstract description 26
- 238000000197 pyrolysis Methods 0.000 claims abstract description 23
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- 240000004808 Saccharomyces cerevisiae Species 0.000 claims description 21
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 238000000498 ball milling Methods 0.000 claims description 13
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- 230000004151 fermentation Effects 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 10
- 239000007864 aqueous solution Substances 0.000 claims description 7
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- 238000004321 preservation Methods 0.000 claims description 2
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- 230000001276 controlling effect Effects 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
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- 229910021641 deionized water Inorganic materials 0.000 description 3
- 239000002019 doping agent Substances 0.000 description 3
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Abstract
The invention belongs to the field of microwave absorbing materials, and particularly relates to a preparation method of a porous carbon particle microwave absorbent with adjustable electromagnetic parameters. The preparation method comprises the following steps: (1) the flour and the carbon fiber are ball-milled and mixed uniformly according to a certain proportion; (2) fermenting and pore-forming by using saccharomycetes and drying; (3) pyrolyzing the dried product in an inert atmosphere; (4) the pyrolysis product is crushed and screened for particles with developed voids. The electromagnetic parameter adjustable porous carbon particle microwave absorbent has a developed pore structure and a large specific surface area, and the electromagnetic parameters can be adjusted by controlling the doping amount of the carbon fibers, so that the wave absorbing performance of the material is improved. The preparation method is simple in preparation process, low in cost, environment-friendly and suitable for industrial production.
Description
Technical Field
The invention belongs to the field of microwave absorbing materials, and particularly relates to a preparation method of a porous carbon particle microwave absorbent with adjustable electromagnetic parameters.
Background
Compared with a magnetic metal microwave absorbent, the porous carbon absorbent has the advantages of light weight, low doping amount, corrosion resistance and the like. However, the porous carbon, especially the porous carbon prepared by biomass pyrolysis, has low conductivity and small dielectric loss to microwaves, so that the microwave absorbing performance of the material can be improved by doping and modifying the porous carbon. Common biomass materials, such as wood, straw, fruit shells and the like, have a fixed pore structure, and are not easily subjected to doping modification before and after pyrolysis so as to regulate and control electromagnetic parameters. Flour, as a powdery biomass material, has a porous structure which is not abundant, but can be endowed with the porous structure through a proper forming and pyrolysis process, and doping modification of the biomass material before pyrolysis is relatively easy. The carbon fiber has light weight and large dielectric constant, can be used as a doping agent to be added into flour, and can improve the dielectric constant of the porous carbon material obtained after pyrolysis on the premise of hardly increasing the specific gravity of the material, thereby improving the wave-absorbing performance of the material.
Flour and carbon fibers can be uniformly mixed through a simple ball milling and mixing process, the flour and carbon fiber mixture is endowed with rich pore structures by gas generated by yeast fermentation, and the pore structures can be reserved in the next pyrolysis process. The disordered structure built by the carbon fibers mixed in the porous carbon not only has a supporting effect on the porous structure in the pyrolysis process, but also can form a conductive network to generate conductive loss on microwaves. The electromagnetic parameters of the pyrolysis product can be well controlled by controlling the doping amount of the carbon fiber, so that the wave-absorbing performance of the material is improved.
Disclosure of Invention
The invention aims to provide a preparation method of a porous carbon particle microwave absorbent with adjustable electromagnetic parameters. The method has the advantages of simple preparation process, low production cost, sustainable development and suitability for industrial production.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a preparation method of a porous carbon particle microwave absorbent with adjustable electromagnetic parameters comprises the following steps:
1) mixing carbon fiber and flour according to the mass ratio WFlour：WCarbon fiber100: (1-20) ball-milling and mixing materials uniformly;
2) adding an aqueous solution containing saccharomycetes into the mixture obtained in the step 1), and uniformly mixing and stirring;
3) fermenting the product obtained in the step 2) for 0.5-10 h at constant temperature;
4) placing the product obtained in the step 3) in a drying oven for drying;
5) putting the dried product obtained in the step 4) into an inert atmosphere for pyrolysis;
6) crushing the pyrolysis product obtained in the step 5), and screening out particles with developed pores.
The preparation method of the porous carbon particle microwave absorbent with adjustable electromagnetic parameters is preferable, and in the step 1), W isFlour：WCarbon fiber＝100：10。
The preparation method of the porous carbon particle microwave absorbent with adjustable electromagnetic parameters comprises the step 1), wherein the ball milling time is 1-10 hours.
The preparation method of the porous carbon particle microwave absorbent with adjustable electromagnetic parameters comprises the following steps in step 2), wherein the aqueous solution containing the yeast comprises the following components in parts by mass: 0.1-0.5 part of dry yeast powder and 100 parts of water; the water solution containing the yeast needs to be stirred and treated for 0.5 to 5 hours under the condition of heating in a water bath at the temperature of 20 to 50 ℃ so as to excite the activity of the yeast.
The preparation method of the porous carbon particle microwave absorbent with adjustable electromagnetic parameters comprises the step 3), wherein the fermentation temperature is 20-50 ℃.
The preparation method of the porous carbon particle microwave absorbent with adjustable electromagnetic parameters comprises the step 4), wherein the drying temperature is 50-150 ℃, and the drying time is 10-20 hours.
The preparation method of the porous carbon particle microwave absorbent with adjustable electromagnetic parameters comprises the following steps in step 5): the heating rate is 2-10 ℃/min, the pyrolysis temperature is 400-1000 ℃, and the heat preservation time is 2-10 h.
Preferably, in the step 5), particles with the particle size of 50-300 meshes are screened out, and the particles are developed in pores and rich in pore structure; the absorbent has a pore size of 10-50 μm and a porosity of 30-50%.
According to the preparation method of the electromagnetic parameter adjustable porous carbon particle microwave absorbent, carbon fibers in the absorbent are uniformly doped in porous carbon, the carbon fibers account for 2-20 wt%, and the balance is porous carbon.
The design idea of the invention is as follows: in the design process of the wave-absorbing material, the loss capacity of the absorbent to incident microwaves and the impedance matching performance between the absorbent and air are in mutual contradiction, the material with high loss often has strong reflection to the microwaves, and the porous material can relieve the contradiction to a certain extent. However, the common porous carbon material prepared by pyrolyzing biomass with a fixed pore structure has low conductivity and is difficult to regulate and control the electromagnetic parameters. The invention creatively selects the powdery biomass flour as the raw material and adopts the carbon fiber as the doping agent to dope the biomass flour before pyrolysis, thereby solving the problem of difficult doping modification of the porous carbon material prepared from the biomass material. The yeast is adopted to replace the traditional chemical reagent to be used as the pore-forming agent, so that the problem of environmental unfriendliness in the preparation process is solved. The finally prepared carbon fiber doped porous carbon particles not only have rich porous structures, but also can regulate and control the electromagnetic parameters of the absorbent by controlling the doping amount of the carbon fibers, thereby improving the wave-absorbing performance. The carbon fiber which is built up disorderly in the porous carbon particles can not only support the porous structure, but also form a conductive network to enhance the conductive loss of incident microwaves.
The invention has the advantages and beneficial effects that:
1. according to the invention, flour is used as a carbon source, carbon fiber is used as a doping agent, simple ball milling and mixing, yeast fermentation and pore forming and high-temperature activation processes are adopted to prepare the porous carbon microwave absorbent with adjustable electromagnetic parameters, the absorbent has a developed pore structure and a large specific surface area, and the electromagnetic parameters can be adjusted by controlling the doping amount of the carbon fiber, so that the wave absorbing performance of the material is improved.
2. Compared with the porous carbon material prepared by traditional biomass pyrolysis, the material prepared by the invention can be doped with carbon fibers through simple ball milling mixing on the premise of light specific gravity and rich pore structure, so that the electromagnetic parameters of the material are well adjusted, and the wave-absorbing performance of the material is improved.
3. The preparation method is simple in preparation process, low in cost, environment-friendly and suitable for industrial production.
Drawings
FIGS. 1(a) -1 (b) are SEM topographs of the inventive materials of example 2. Fig. 1(b) is a partially enlarged view of fig. 1 (a).
Figure 2 is an electromagnetic parameter (20 wt.% doping) of the inventive material of example 2; in the figure, the abscissa f represents the frequency (GHz), and the ordinate ε 'is the real part of the complex permittivity, ε' is the imaginary part of the complex permittivity, μ 'is the real part of the complex permeability, and μ' is the imaginary part of the complex permeability.
Detailed Description
In the specific implementation process, the preparation method of the electromagnetic parameter adjustable porous carbon particle microwave absorbent specifically comprises the following steps: (1) the flour and the carbon fiber are ball-milled and mixed uniformly according to a certain proportion; (2) fermenting and pore-forming by using saccharomycetes at constant temperature and drying; (3) pyrolyzing the dried product in an inert atmosphere; (4) the pyrolysis product is crushed and screened for particles with developed voids.
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. Other embodiments, which can be derived by one of ordinary skill in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
In this embodiment, a preparation method of a porous carbon particle microwave absorbent with adjustable electromagnetic parameters includes the following steps:
step 1: mixing flour and carbon fiber; 100g of flour and 2g of carbon fiber (W) were weighed out separatelyFlour：WCarbon fiber100: 2) putting the mixture into a ball milling tank, and ball milling the mixture for 5 hours.
Step 2: preparing an aqueous solution containing yeast; 0.3g of dried yeast powder is dispersed in 100ml of deionized water and stirred in a water bath at 30 ℃ for 0.5h to fully stimulate the activity of the yeast.
And step 3: fermenting and pore-forming by using saccharomycetes; and (3) pouring the water solution containing the microzyme obtained in the step (2) into the mixed powder in the step (1), uniformly mixing and stirring, and fermenting for 1h in a drying oven at constant temperature of 40 ℃.
And 4, step 4: drying the fermentation product; and (4) putting the fermentation product obtained in the step (3) into a drying box, and drying for 12h at the temperature of 120 ℃.
And 5: pyrolysis of the dried product; and (4) putting the dried product obtained in the step (4) into an alumina crucible, heating to 800 ℃ at the heating rate of 2 ℃/min under the protection of argon, preserving heat for 2 hours, and cooling to room temperature along with the furnace to obtain the carbon fiber doped porous carbon.
Step 6: preparing carbon fiber doped porous carbon particles; and (5) crushing the carbon fiber doped porous carbon obtained in the step (5) by using a mortar, and screening out particles with the particle size of 50 meshes and developed pores. In this example, the pore size of the absorber was about 20 μm and the porosity was about 40%. The carbon fiber in the absorbent is uniformly doped in porous carbon, the carbon fiber accounts for 5 wt.%, and the rest is porous carbon.
In this example, the porous carbon particle microwave absorbent has the following properties: when the doping amount is 20 wt.%, and the matching thickness is 3.5mm, the maximum effective absorption bandwidth is 3 GHz; at a matching thickness of 4.5mm, a minimum reflectance value of-38.7 dB was obtained at 6.1 GHz.
Example 2
In this embodiment, a preparation method of a porous carbon particle microwave absorbent with adjustable electromagnetic parameters includes the following steps:
step 1: mixing flour and carbon fiber(ii) a 100g of flour and 5g of carbon fiber (W) were weighed out separatelyFlour：WCarbon fiber100: 5) putting the mixture into a ball milling tank, and ball milling and mixing the mixture for 6 hours.
Step 2: an aqueous solution containing yeast is prepared. 0.3g of dried yeast powder is dispersed in 100ml of deionized water and stirred in a water bath at 35 ℃ for 0.5h to fully stimulate the activity of the yeast.
And step 3: fermenting and pore-forming by using saccharomycetes; and (3) pouring the water solution containing the microzyme obtained in the step (2) into the mixed powder in the step (1), uniformly mixing and stirring, and fermenting for 1h in a drying oven at the constant temperature of 35 ℃.
And 4, step 4: drying the fermentation product; and (4) putting the fermentation product obtained in the step (3) into a drying box, and drying for 12h at 110 ℃.
And 5: pyrolysis of the dried product; and (4) putting the fermentation product obtained in the step (4) into an alumina crucible, heating to 900 ℃ at the heating rate of 5 ℃/min under the protection of argon, preserving heat for 3 hours, and cooling to room temperature along with the furnace to obtain the carbon fiber doped porous carbon.
Step 6: preparing carbon fiber doped porous carbon particles; and (5) crushing the carbon fiber doped porous carbon obtained in the step (5) by using a mortar, and screening out particles with the particle size of 100 meshes and developed pores. In this example, the pore size of the absorber was about 20 μm and the porosity was about 30%. The carbon fiber in the absorbent is uniformly doped in porous carbon, the carbon fiber accounts for about 10 wt.%, and the rest is porous carbon.
SEM photographs of the porous carbon particles prepared in example 2 were taken as shown in fig. 1(a) to 1 (b). As can be seen from the figure, the particle size is about 300 μm, the particle has a rich pore structure, and the pore diameter is about 20 μm; the diameter of the carbon fiber doped in the porous carbon particles is about 5 μm, and the carbon fiber is in a state of disordered interweaving arrangement.
As shown in FIG. 2, the sample of the microwave absorbent with porous carbon particles obtained in example 2 and paraffin were mixed in a mass ratio WSample (I)：WParaffin wax2: 8 electromagnetic parameter profile measured after doping. As can be seen from the graph, the real part of the dielectric constant of the sample shows reduced fluctuation along with the increase of the frequency in the range of 13-7, and the imaginary part shows reduced fluctuation along with the increase of the frequency in the range of 5.5-3, which indicates that the sample has better dielectric loss(ii) a The real part of the permeability is approximately 1 and the imaginary part is approximately 0, which indicates that the sample has no magnetic loss.
In this example, the porous carbon particle microwave absorbent has the following properties: when the doping amount is 20 wt.%, and the matching thickness is 2mm, the maximum effective absorption bandwidth is 5.1 GHz; at a matching thickness of 4mm, a minimum reflectance value of-47.8 dB was obtained at 5.9 GHz.
Example 3
In this embodiment, a preparation method of a porous carbon particle microwave absorbent with adjustable electromagnetic parameters includes the following steps:
step 1: mixing flour and carbon fiber; 100g of flour and 10g of carbon fibers (W flour: W carbon fibers: 100: 10) are respectively weighed and put into a ball milling pot, and the materials are mixed for 5 hours in a ball milling mode.
Step 2: preparing an aqueous solution containing yeast; 0.3g of dried yeast powder is dispersed in 100ml of deionized water and stirred in a water bath at 40 ℃ for 0.5h to fully stimulate the activity of the yeast.
And step 3: fermenting and pore-forming by using saccharomycetes; and (3) pouring the water solution containing the microzyme obtained in the step (2) into the mixed powder in the step (1), uniformly mixing and stirring, and fermenting for 1h in a drying oven at constant temperature of 30 ℃.
And 4, step 4: drying the fermentation product; and (4) putting the fermentation product obtained in the step (3) into a drying box, and drying for 12h at the temperature of 130 ℃.
And 5: pyrolysis of the dried product; and (4) putting the fermentation product obtained in the step (4) into an alumina crucible, heating to 1000 ℃ at the heating rate of 10 ℃/min under the protection of argon, preserving heat for 5 hours, and cooling to room temperature along with the furnace to obtain the carbon fiber doped porous carbon.
Step 6: preparing carbon fiber doped porous carbon particles; and (5) crushing the carbon fiber doped porous carbon obtained in the step (5) by using a mortar, and screening out particles with the particle size of 200 meshes and developed pores. In this example, the pore size of the absorbent was about 10 μm and the porosity was about 30%. The carbon fiber in the absorbent is uniformly doped in the porous carbon, the carbon fiber accounts for 20 wt.%, and the rest is the porous carbon.
In this example, the porous carbon particle microwave absorbent has the following properties: when the doping amount is 20 wt.%, and the matching thickness is 2mm, the maximum effective absorption bandwidth is 3.8 GHz; with a matching thickness of 1.5mm, a minimum reflectance value of-26.4 dB was obtained at 16.1 GHz.
The embodiment result shows that the porous carbon particle microwave absorbent doped with the carbon fibers is prepared by mixing the carbon fibers in the flour, fermenting and forming pores by using yeast bacteria and finally performing pyrolysis in an inert atmosphere, and the electromagnetic parameters of the absorbent can be regulated and controlled by controlling the mixing amount of the carbon fibers. The porous carbon particles prepared by the method have high porosity, light specific gravity and adjustable electromagnetic parameters, and are a microwave absorbent with excellent performance.
Claims (9)
1. A preparation method of a porous carbon particle microwave absorbent with adjustable electromagnetic parameters is characterized by comprising the following steps:
1) mixing carbon fiber and flour according to the mass ratio WFlour：WCarbon fiber100: (1-20) ball-milling and mixing materials uniformly;
2) adding an aqueous solution containing saccharomycetes into the mixture obtained in the step 1), and uniformly mixing and stirring;
3) fermenting the product obtained in the step 2) for 0.5-10 h at constant temperature;
4) placing the product obtained in the step 3) in a drying oven for drying;
5) putting the dried product obtained in the step 4) into an inert atmosphere for pyrolysis;
6) crushing the pyrolysis product obtained in the step 5), and screening out particles with developed pores.
2. The method for preparing the porous carbon particle microwave absorbent with adjustable electromagnetic parameters according to claim 1, wherein preferably, in the step 1), W isFlour：WCarbon fiber＝100：10。
3. The preparation method of the porous carbon particle microwave absorbent with adjustable electromagnetic parameters according to claim 1, wherein in the step 1), the ball milling time is 1-10 h.
4. The preparation method of the porous carbon particle microwave absorbent with adjustable electromagnetic parameters according to claim 1, wherein in the step 2), the aqueous solution containing the yeast comprises the following components in parts by mass: 0.1-0.5 part of dry yeast powder and 100 parts of water; the water solution containing the yeast needs to be stirred and treated for 0.5 to 5 hours under the condition of heating in a water bath at the temperature of 20 to 50 ℃ so as to excite the activity of the yeast.
5. The preparation method of the porous carbon particle microwave absorbent with adjustable electromagnetic parameters according to claim 1, wherein in the step 3), the fermentation temperature is 20-50 ℃.
6. The preparation method of the porous carbon particle microwave absorbent with adjustable electromagnetic parameters, according to claim 1, characterized in that in the step 4), the drying temperature is 50-150 ℃ and the drying time is 10-20 h.
7. The method for preparing the porous carbon particle microwave absorbent with adjustable electromagnetic parameters according to claim 1, wherein in the step 5), the pyrolysis process comprises: the heating rate is 2-10 ℃/min, the pyrolysis temperature is 400-1000 ℃, and the heat preservation time is 2-10 h.
8. The preparation method of the porous carbon particle microwave absorbent with adjustable electromagnetic parameters according to claim 1, characterized by preferably, in the step 5), screening out particles with a particle size of 50-300 meshes, wherein the particles have developed pores and rich pore structures; the absorbent has a pore size of 10-50 μm and a porosity of 30-50%.
9. The preparation method of the electromagnetic parameter adjustable porous carbon particle microwave absorbent according to claim 1, wherein the carbon fibers in the absorbent are uniformly doped in the porous carbon, the carbon fibers account for 2-20 wt.%, and the balance is the porous carbon.
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